Yarn materials and fibers including starch-based polymeric materials

Abstract

Described are very high molecular weight (e.g., over 2 million, such as 3-20 million g/mol) starch-based materials, and formulations including such, which can be spun in spunbond, melt blown, yarn, or similar processes. Even with such very high molecular weights, the formulations can be processed at commercial line speeds, with spinneret shear viscosities of 1000 sec−1, without onset of melt flow instability. The starch-based material can be blended with one or more thermoplastic materials having higher melt flow index value(s), which serve as a diluent and plasticizer, allowing the very viscous starch-based component to be spun under such conditions. The particular melt flow index characteristics of the thermoplastic diluent material can be selected based on what type of process is being used (e.g., spunbond, melt blown, yarn, etc.). The starch-based material may exhibit high shear sensitivity, strain hardening behavior, and/or very high critical shear stress (e.g., at least 125 kPa).

The invention claimed is: 
     
       1. A method for producing yarn fibers from a composition that includes a starch-based polymeric material, the method comprising:
 providing a composition that includes a starch-based polymeric material; 
 spinning the composition to produce yarn fibers having an as spun diameter from about 40 μm to about 150 μm, the yarn fibers including the starch-based polymeric material, wherein the composition exhibits a shear viscosity of greater than 50 Pa·s and no more than about 600 Pa·s at 190° C. at a process shear rate of 200 s −1 , and avoids onset of melt flow instability during spinning of the yarn fibers; and 
 drawing the as spun yarn fibers from their spun diameter down to a smaller diameter. 
 
     
     
       2. The method of  claim 1 , wherein the smaller diameter after drawing the yarn fibers is from 10 μm to 50 μm. 
     
     
       3. The method of  claim 1 , wherein the starch-based polymeric material is a high molecular weight starch-based polymeric material having an average molecular weight of at least 3 million g/mol. 
     
     
       4. The method of  claim 1 , wherein the composition is a blend of the starch-based polymeric material and at least one thermoplastic polymer. 
     
     
       5. The method of  claim 4 , wherein the at least one thermoplastic polymer includes a polymer having a melt flow index as measured at 230° C. under a load of 2.16 kg, of from 10 g/10 min to 100 g/10 min. 
     
     
       6. The method of  claim 4 , wherein the starch-based polymeric material is provided in the form of a masterbatch, pre-blended with a first thermoplastic polymer, the method further comprising blending the masterbatch with a second thermoplastic polymer, wherein the first and second thermoplastic polymers have different melt flow index values. 
     
     
       7. The method of  claim 6 , wherein the starch-based polymeric material is included in the masterbatch in an amount of up to 60%, and the starch-based polymeric material is included in the composition that is spun in an amount of up to 40% by weight. 
     
     
       8. The method of  claim 4 , wherein the at least one thermoplastic polymer comprises a grade of polypropylene with both isotactic and atactic structures, having a melt flow index as measured at 230° C. under a load of 2.16 kg, of less than 1000 g/10 min. 
     
     
       9. The method of  claim 1 , wherein the starch-based polymeric material has a water content, including any bound water, of no more than 2%. 
     
     
       10. The method of  claim 1 , wherein the starch-based polymeric material is included in the composition in an amount of up to 60%. 
     
     
       11. The method of  claim 1 , wherein the starch-based polymeric material has a weight average molecular weight of from 3 million g/mol to 20 million g/mol. 
     
     
       12. The method of  claim 1 , wherein the starch-based polymeric material is a high molecular weight starch-based polymeric material having a weight average molecular weight of at least 5 million g/mol. 
     
     
       13. The method of  claim 1 , wherein the starch-based polymeric material is included in the composition that is spun in an amount of up to 40% by weight. 
     
     
       14. The method of  claim 1 , wherein the starch-based polymeric material is included in the composition that is spun in an amount of from 1% to 35% by weight. 
     
     
       15. The method of  claim 1 , wherein the starch-based polymeric material has a weight average molecular weight of from 5 million g/mol to 16 million g/mol. 
     
     
       16. The method of  claim 1 , wherein the starch-based polymeric material has a weight average molecular weight of from 3 million g/mol to 10 million g/mol. 
     
     
       17. The method of  claim 1 , wherein the starch-based polymeric material has a weight average molecular weight of from 5 million g/mol to 7 million g/mol. 
     
     
       18. The method of  claim 1 , wherein the starch-based material has a crystallinity of less than about 20%, and resists recrystallization, and has a water content no greater than 2% by weight. 
     
     
       19. The method of  claim 1 , wherein the composition exhibits a shear viscosity of at least 175 Pa·s and no more than about 600 Pa·s at 190° C. at a process shear rate of 200 s −1 . 
     
     
       20. A method for producing yarn fibers from a composition that includes a starch-based polymeric material, the method comprising:
 providing a composition that includes a starch-based polymeric material, wherein the starch-based polymeric material is a high molecular weight starch-based polymeric material having an average molecular weight of at least 3 million g/mol; 
 spinning the composition to produce yarn fibers having an as spun diameter from about 40 μm to about 150 μm, the yarn fibers including the starch-based polymeric material, wherein the composition exhibits a shear viscosity of greater than 50 Pa·s and no more than about 600 Pa·s at 190° C. at a process shear rate of 200 s −1 , and avoids onset of melt flow instability during spinning of the yarn fibers; and 
 drawing the as spun yarn fibers from their spun diameter down to a smaller diameter. 
 
     
     
       21. The method of  claim 20 , wherein the starch-based polymeric material has a crystallinity of less than about 20%, and resists recrystallization, and has a water content of no greater than 2% by weight, including any bound water. 
     
     
       22. The method of  claim 20 , wherein the starch-based polymeric material is included in the composition that is spun in an amount of up to 60% by weight. 
     
     
       23. The method of  claim 20 , wherein the starch-based polymeric material is included in the composition that is spun in an amount of up to 40% by weight. 
     
     
       24. The method of  claim 20 , wherein the starch-based polymeric material is included in the composition that is spun in an amount of from 1% to 35% by weight. 
     
     
       25. A method for producing yarn fibers from a composition that includes a starch-based polymeric material, the method comprising:
 providing a composition that includes a starch-based polymeric material, wherein the starch-based polymeric material is a high molecular weight starch-based polymeric material having an average molecular weight of at least 3 million g/mol, and wherein the starch-based material has a crystallinity of less than about 20%, and resists recrystallization, and has a water content no greater than 2% by weight; 
 spinning the composition to produce yarn fibers having an as spun diameter from about 40 μm to about 150 μm, the yarn fibers including the starch-based polymeric material, wherein the composition exhibits a shear viscosity of greater than 50 Pa·s and no more than about 600 Pa·s at 190° C. at a process shear rate of 200 s −1 , and avoids onset of melt flow instability during spinning of the yarn fibers; and 
 drawing the as spun yarn fibers from their spun diameter down to a smaller diameter. 
 
     
     
       26. The method of  claim 25 , wherein the composition exhibits a shear viscosity of at least 175 Pa·s and no more than about 600 Pa·s at 190° C. at a process shear rate of 200 s −1 .